1. Field of the Invention
The present invention relates to an image forming apparatus, or, in detail, to an image forming apparatus such as a digital copying machine which can store image information.
2. Description of the Prior Art
In a digital copying machine, a document image is read by a sensor and is stored in a memory. Then, the image data stored in the memory can be processed in various ways. For example, a plurality of the same document image can be reproduced by reading the image data iteratively. It is possible to scale up and down the document image by processing the image data. It is also possible to rotate the document image. A digital copying machine is also known to form document images on front and back faces of a paper in a two-face copy mode. It is also known that a margin can be set when a document image is reproduced. It is also proposed that a plurality of pages of document images are reproduced in a paper by using image data stored in a memory.
However, if a digital copying machine has these various modes in combination, many problems have to be solved. For example, when document images are formed on two faces of a paper, a direction of the two images are set usually to be the same. However, the same direction is not always appropriate. For example, as shown in FIG. 1, four documents having characters "A", "B", "C" and "D" along longitudinal directions thereof are stacked in an automatic document feeder. Then, document images are reproduced on two faces of paper successively so that a direction of the two images are set to be the same. Thus, the two document images having characters "A" and "B" are formed on front and back faces of a paper, while the two document images having characters "C" and "D" are formed on front and back faces of another paper. In a case shown in FIG. 2A, the two papers are bound at the left side. In this case, as shown in FIG. 2B, when the papers are turned over, a reader observes normal images "B" and "C". In another case shown in FIG. 3A, the two papers are bound at the top side. In this case, as shown in FIG. 3B, when the papers are turned over, a reader observes a normal image "B" and an abnormal "C". In the image of "B", top and bottom are reversed and right and left are also reversed.
The documents shown in FIG. 1 are portrait documents where images are formed in longitudinal documents. A portrait document denotes a document which has an image longer along the longitudinal direction. As shown in FIG. 4, if these portrait documents are reproduced in a 2-in-1 mode and in two-face mode, two images are formed as shown in FIG. 5A. That is, document images including "A" and "B" are formed side by side on a front page, while document images including "A" and "B" are formed side by side on a back page. In a case shown in FIG. 5A, papers are bound at the left side. In this case, as shown in FIG. 5B, when the papers are turned over, a reader observes normal images "C", "D" and the like. In another case shown in FIG. 6A, papers are bound at the top side. In this case, as shown in FIG. 6B, when the papers are turned over, a reader observes abnormal images of "C" and "D" where top and bottom are reversed and right and left are also reversed.
If a digital copying machine has modes such as two-face mode, 2-in-1 mode, scale up and down mode, rotation mode and margin mode in combination, similar problems have to be solved. Therefore, it is desirable that the direction of document image can be changed appropriately in two face copy mode.